Generally, for keeping proper function of an engine for vehicles, there is a need to change the lubricating oil periodically or non-periodically. For this purpose, usually a drain port is provided in the oil pan of the engine and such drain port is closed by a plug. However, according to such type of drain plug, if the plug is inadvertently removed when changing the lubricating oil, the lubricating oil in the oil pan may spill or scatter away to soil the worker's clothes or the floor of the workshop. Also, repeated use (fitting and removal) of such drain plug may result in a loose fit, and careless fixing of such plug may cause imperfect sealing to give rise to dangerous leaking of the lubricating oil.
For overcoming such problem, it has been attempted to adapt a shut-off valve at the drain port, but such attempt has practically ended in failure because mere incorporation of such a shut-off valve could not eliminate the risk of a chance opening of the valve by vibration of the vehicle.
Therefore, a change of the lubricating oil is usually practiced by inserting into the oil pan an end of an oil hose connected to a manually operatable oil pump. It is however difficult for the ordinary household to be equipped with such an oil pump, so that the oil change is usually practiced as a commercial deal at a filling station or a repair shop. This, however, involves some serious problems such as fairly high cost of oil change at such places and impracticality for a resident at a backcountry to go all the way to a repair shop for the only purpose of an oil change.